Facebook's News Feed Algorithm

“Our goal is to build the perfect personalized newspaper for every person in the world,” Facebook CEO Mark Zuckerberg said in a public Q&A in 2014. “We’re trying to personalize it and show you the stuff that’s going to be most interesting to you.”

That's what Facebook's News Feed has been about since the very beginning. According to Zuckerberg, each of us gets exposed to more than 1,500 stories each day, but an average user only gets to see about 100 stories a day on their News Feed.

To give these users the best experience possible, Zuckerberg and his team of engineers are constantly learning user behavior and picking up signals that show what kind of content each user is most interested in.

How It Works

The Like button has always been the epicenter of Facebook's user experience -- not only because we see it on everyone's posts, but also because it allows us to personalize our own experience (and influence everyone else's). Since it was first introduced in November 2007, it's helped Facebook's engineers figure out which posts were delighting users, boring them, offending them, and so on.

Nowadays, the algorithm that governs Facebook's News Feed has grown to be much more sophisticated. It isn't just about the Like button anymore -- and not just because reaction buttons are now in the mix. In fact, Facebook's algorithm is by far the most complicated of the three social networks covered in this post.

Here's a quick rundown of the most important things Facebook's algorithm takes into account.

Relevancy Score

When picking posts for each person who logs on to Facebook, the News Feed algorithm takes into account literally hundreds of variables -- and can predict whether a given user will Like, click, comment, share, hide, or even mark a post as spam.

More specifically, the algorithm predicts each of these outcomes with a certain degree of confidence. This prediction is quantified into a single number called a "relevancy score" that's specific both to you and to that post.

Once every post that could potentially show up in your feed has been assigned a relevancy score, Facebook's sorting algorithm ranks them and puts them in the order they end up appearing in your feed. This means that every time you log in, the post you see at the very top of your News Feed was chosen over thousands of others as the one most likely to make you react and engage.

Ads are given relevancy scores, too, so that Facebook can show users only the ads that could matter most to them. Again, this is supposed to give users a better experience -- but it's also helpful for the businesses that are paying for the ads. It's calculated based on the positive feedback (video views, conversions, etc.) and negative feedback Facebook expects an ad to receive from its target audience. (Learn more about relevancy score for Facebook ads here.)

Prioritizing Friends

Before 2015, Facebook was predicting what users want to see on the News Feed based on more indirect signals, like Likes, comments, and shares of others. Eventually, they added options for users to filter out posts they don't want to see. But what about helping boost the posts users do want to see?

Through studies and surveys, they found that many users were concerned they were missing important updates from friends they cared about the most. In response to these concerns, they began changing the News Feed algorithm to give more control to the users themselves.

It started in April 2015, when they began giving priority (in the form of higher relevancy scores) to posts from friends over the Pages they follow and promotional posts. Later that year, in July, they introduced the "See First" feature, which lets you actually hand-pick which accounts -- whether friends or followed Pages -- you want to see first at the top of your News Feed.

Now, when you select a person or page to "see first," their posts will appear at the top of your News Feed. (Note: Selecting people to "see first" is different than selecting them as a close friend: When you select a person as a close friend, you'll just receive notifications when they post something new.)

To select people or pages to "see first": First, click the downward facing arrow in the top-right corner of any Facebook page and select "News Feed Preferences."

In the window that appears, click "Prioritize who to see first." Then, select the people or pages you'd like to, see first on your feed.

Time Spent on a Post

Starting in June 2015, Facebook started monitoring how much time users spend viewing certain posts. Of course, the time you spend on a post can vary depending on your internet speed, the length of the post, and so on -- and the folks at Facebook are aware of that.

However, they have found that if people are spending a lot more time on a particular post in their feed than the majority of other posts they look at, then it's a good sign the content was relevant to them.

How does this play out in the feed? If you spend more time on a particular post, Facebook is more likely to show that post on your friends’ News Feeds.

Video Engagement

In summer 2015, Facebook surveyed users on how they interacted with video on their News Feeds and found that many people who were interested in a given video didn't necessarily Like it, comment on it, or share it with their friends. Since engagement is one of the primary ways Facebook measures people's interest in posts, they had to come up with other ways to figure out whether people enjoyed the videos they were seeing.

To help do that, they started monitoring other forms of video engagement -- like turning on the audio, switching to full-screen mode, or enabling high definition. So if you turn up the volume on a video or make it full-screen, the algorithm will interpret that as you enjoying the video, and will show you similar videos higher up in your feed.

The update doesn't mean users will see more videos in their News Feed -- only those who already engage more with video-related content.

Facebook's algorithm is very, very complex, but we hope that gives you a good idea of what it considers important.